1. Field of the Invention
The present invention relates to a method and apparatus for information processing which support co-operative work on one or more computers.
2. Description of the Related Art
Recently, as the penetration of high-speed LAN and WAN increases, a system (groupware in a narrow sense) has been proposed and actually utilized in which a place for simultaneous work by a plurality of users is implemented on computers by linking and operating various application programs on a plurality of computers connected by a network. In such a system, data, such as images and documents, and resources such as application programs, are shared and utilized by a plurality of users. If the operation of resources is performed simultaneously by a plurality of users, it becomes difficult to maintain the consistency of the contents of the data and the state of the application, and operate the system correctly. For this reason, a mechanism for avoiding a conflicts in the users' references and operations of the shared resource is needed.
In order to implement such a mechanism, two methods have been proposed: one is an access right control method and the other is a floor control method.
The access right control method is one in which the resource is regarded as data, such as images and documents, and an access right (the right to access and modify data) is specified in respect of each user. Each user can work with only the data to which he has an access right. A method based on an access control list and a capability list is commonly used (See "Operating Systems: Design and Implementation. ANDRAEW S. TANENBAUM, Prentice-Hall, 1987" etc. for the access control list and capability list).
On the other hand, according to the floor control method, an application is regarded as a resource, and a floor (the right to operate the application) is given to the user in accordance with the different circumstances. Only the user (or the application as an agency thereof) having the floor can perform an operation on the system.
The access right control method is utilized in systems which provide a relatively simple structure and only a few operation (or calculation) systems. A file system in a UNIX (trade mark) operating system is a typical example in which the access right control method is applied.
On the other hand, the floor control method is utilized in systems in which the operation of a complicated application program which can change dynamically as circumstances demand is required. For this reason, a resource control method based on the floor control method is mainly used in groupware systems.
However, the above-described two methods are not at all exclusive methods, and there is a system in which the access right control method is utilized as a part of a mechanism for determining the floor in the resource control method. Since many operating systems provide file systems with an access right control methods, the floor control method constructed thereon can utilize the access right control system.
Conventionally, a floor control method suitable for a groupware system has been implemented by incorporating the mechanism of the floor control separately in each application operated on the groupware system. In many cases, incorporation is adopted in which one process for effecting centralized control of the floor is provided, and each application acquires or releases the floor by communication with the floor control server.
However, the conventional floor control method raises the following problems:
1) Since the floor control mechanism must be packaged on each of the applications, the application program becomes complicated. Thus, it is difficult to develop the application. PA1 2) It is difficult to implement the floor control among the different applications. PA1 3) Since entities which compete with each other for the floor are restricted to the application program, it is difficult to employ a specific operation and a module to be incorporated dynamically as objects of the floor control.